A cab style of a cab-over-engine truck affects automobile performances, such as a fuel consumption ratio. From an aspect of improvement of aerodynamic characteristics in a driving condition of the vehicle, various kinds of researches or studies have been carried out for long years, with respect to configurations of cabs or flush surface contours of vehicle bodies for reducing the air resistance, devices for reducing the air resistance, or the like. An excessively angled or inclined front-windshield results in reduction of an internal space of the cab, and therefore, in this kind of researches or studies, attempts have been made to improve the aerodynamic characteristics, based on square configurations of the cab.
An air deflector is known in the art, as a device reducing the air resistance for improving the aerodynamic characteristics of the vehicle in its driving condition. Such an air deflector is also called, a wind deflector or a drag-foiler. This kind of air deflector is disclosed in, for instance, Japanese patent laid-open publication No. 11-115828, Japanese patent publication No. 3309603, or Japanese utility-model publication No. 2547461. As disclosed in these publications, the air deflector is attached onto a roof of a cab of a cab-over-engine truck so as to reduce the air resistance during driving for improving its aerodynamic characteristics.
FIGS. 8A and 8B are a front elevational view and a partial side elevational view exemplifying an arrangement of a cab-over-engine truck provided with a conventional air deflector.
As shown in FIGS. 8A and 8B, a truck 51 is provided with an air deflector 55 and a gap sealing member 56. The air deflector 55 is mounted on a roof of the cab 52. The gap sealing member 56 is arranged to close a gap formed between a cab 52 and a van body 53. The air deflector 55 eliminates a stepped formation or a difference in level between the roof of the cab 52 and a vertical front face 54 of the van body 53, so that a flow of air, as indicated by an arrow A, is regulated and smoothly deflected by the air deflector 55. In a driving condition of the vehicle, the flow of air A is directed from a front face of the cab 52 along top and side faces of the van body 53 toward the rear of the vehicle. Further, the gap sealing member 56 eliminates the gap and a stepped formation between side faces of the cab 52 and the front face 54 to some extent. Similarly to the air deflector 55, the member 56 also causes the flow of air A to be regulated and smoothly deflected, so that the flow A is directed along the side faces of the van body 53. In the cab-over-engine truck provided with the air deflector 55 and the gap sealing member 56, effects of regulation and deflection of the airflow A are to be obtained by the air deflector 55 and the member 56, and therefore, the air resistance acting on the vehicle in its driving condition can be reduced. In general, it is considered that improvement of the aerodynamic characteristics by the air deflector 55 and the member 56 allows the fuel consumption ratio to be reduced by a few per cent.
However, right and left marker lamps 57 in a pair are installed on upper corners of the vertical front face 54, in a case of a vehicle provided with a box-type van body, such as a dry van body or wing body. The marker lamp 57 is mainly intended to function as a target or indication for recognizing positional relation between oncoming vehicles. Therefore, the devices for reducing the air resistance, such as the air deflector 55 and the gap sealing member 56, have to be designed to ensure visibility of the marker lamps 57, and the positions and configurations of such devices should be so set as to prevent the markers from being concealed. That is, the device for reducing the air resistance, such as the air deflector, cannot conceal the upper corner areas of the front face 54 against the flow of air A, but it can be merely designed to cover the upper part of the front face 54 except for the corner areas. Therefore, the flow of air A impinges on the corner areas of the front face 54 during driving, so that abrupt direction change or turbulence of the airflow A is caused. This results in increase of the air resistance and inferiority of the aerodynamic performance of the vehicle.